The objective of this study is to understand how spatiotemporal and kinetic gait parameters are associated with bone health in pwSMA who are receiving DMT. We hypothesize that gait parameters are associated with BMD and can determine fracture risk in pwSMA. This is an observational study that involves one in-clinic visit (approximately 3 hours) with remote follow-up visits (approximately 15 minutes) every 3 months for 1 year to collect fracture and medical history. Each of the assessments included in this study are non-interventional and are not intended as a treatment nor are they at the level of standard of care.